182 MR. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 
exceeding the breadth of the two tuberosities, in which respect Simia differs from both 
Man and Troglodytes (Pl. XXXVI. figs. 5 & 6). 
The posterior projection of the head is greater than in Man and the Gorilla, the 
bone immediately below the posterior part of the margin of the articular surface being 
more concave (Pl. XXXVI. fig. 4). The anatomical neck is more marked than in the 
higher forms, especially than in Man, and the head rises more above the summit of the 
radial (greater) tuberosity. 
The angle formed by the groove separating the last-named tuberosity from the head, 
with a line connecting the two condyles, is in general much more acute than in Man 
and Troglodytes. There is nevertheless considerable individual variation, the angle 
being sometimes as near a right angle as in the Gorilla (Pl. XXXVI. fig. 5), while in 
other instances (Pl. XXXVI. fig. 6) it is only about 34°; yet, in all the specimens of 
Simia which I have examined, the head looks more directly backwards and less 
inwards than in Man and Troglodytes. 
The radial tuberosity in the Orang is less prominent than in the Gorilla, and but 
little more so than in Man, though the surface for the teres minor is more sharply 
‘defined than in the higher forms (Pl. XXXVI. fig. 3). The surface for the infra- 
spinatus looks more outwards and less upwards than in Man (Pl. XXXVL. fig. 3). 
The ulnar, a smaller tuberosity, has its upper part next the bicipital groove less 
prominent than in Man or Zroglodytes. Sometimes its lower part is more prominent 
than its upper portion. ‘This tuberosity is more nearly approached by the margin of 
the articular surface of the head than in the higher forms; so that there is a small deep 
pit (Pl. XXXVI. fig. 4) between them, instead of a rather wide and slightly concave 
surface. 
When the humerus is vertical, and its anterior surface opposite the observer, the 
ulnar tuberosity generally hides part of the lower margin of the neck of the bone, 
in which respect Simia resembles Zroglodytes and differs from Man‘. As in higher 
forms, no part of the head of the humerus is so hidden in the Orang. : 
At the lower end of the bone the ulnar, or inner, condyle is not so prominent as in 
Man or Troglodytes, nor does it extend so much downwards as in Man and the Chim- 
panzee, but appears as if it had been truncated obliquely from below upwards and 
ulnad, though this appearance is not so marked as in the Gorilla, on account of the 
less prominence of the condyle in the Orang. As in Troglodytes, there is not that 
concavity on its posterior surface which is more or less marked in Man. 
The external, or radial, condyle is much as in Man and the Chimpanzee, and its most 
prominent point is situated lower down than in the Gorilla. 
The inferior articular surface of the humerus is almost quite as in Man, except that 
its innermost part generally descends less below the rest of the surface than in him 
or the Chimpanzee, though more so than sometimes is the case in the Gorilla. 
' Owen, Trans. Zool. Soc. vol. y. p. 4, pl. 3. figs. 1, 5, 8. 
